1. Technical Invention
The present invention generally relates to color filters, and more particularly to a method for manufacturing a color filter.
2. Discussion of Related Art
At present, liquid crystal displays (LCDs) are used in various fields, such as for notebook PCs, mobile phones, desktop monitors, and digital cameras, because of their excellent characteristics, such as low weight, thinness, and low power consumption. The liquid crystal display includes a color filter for displaying color images. For the device to have color capability, each pixel is aligned with a color area, typically red, green, or blue, of a color filter array. Depending upon the image to be displayed, one or more of the pixel electrodes is energized during display operation to allow full light, no light, or partial light to be transmitted through the color filter area associated with that pixel. The image perceived by a user is a blend of colors formed by the transmission of light through adjacent color filter areas.
Referring to FIG. 1, a flow chart of a conventional ink-jet method for manufacturing a color filter is shown. The method mainly includes the steps of: forming a metallic material layer on a transparent substrate and a first photoresist layer on the metallic material layer; exposing the first photoresist layer using a photo-mask; developing the first photoresist layer to form a patterned photoresist matrix; etching the metallic material layer to form a black matrix and removing the residual first photoresist layer; forming a second photoresist layer on the transparent substrate thereby covering the black matrix with the second photoresist layer; irradiating a surface of the transparent substrate facing away from the second photoresist layer so as to expose the second photoresist layer; developing the second photoresist layer to form a plurality of banks on the black matrix; injecting ink into spaces defined by the banks and the black matrix using an ink-jet device; and solidifying the ink.
Referring to FIGS. 2 to 9, more-detail steps of the conventional ink-jet method are shown. Referring to FIG. 2, a transparent substrate 100 is provided. A metallic material layer 102 and a first photoresist layer 104 are formed on the transparent substrate 100 in turn. The metallic material layer 102 is a chromium film layer or a chromium alloy film layer and is generally formed by evaporation or sputtering process.
Referring to FIG. 3, the first photoresist layer 104 is exposed using a photo-mask (not shown) and then developed to form a patterned photoresist matrix 1041. Therefore, the pattern of the photo-mask is transferred to the patterned photoresist matrix 1041.
Referring to FIG. 4, the metallic material layer 102 is etched to form a black matrix 1021 on the transparent substrate 100, and then the patterned photoresist matrix 1041 is totally removed. Therefore, the pattern of the patterned photoresist matrix is transferred to the black matrix 1021.
Referring to FIG. 5, a second photoresist layer 106 is formed on the transparent substrate 100 thereby covering the black matrix 1021 with the second photoresist layer 106. U.V. (ultraviolet) radiation emitted from an ultraviolet light source 112 is then transmitted onto a surface of the transparent substrate 100 facing away from the second photoresist layer 106 so as to expose the second photoresist layer 106.
Referring to FIG. 6, the photoresist layer 106 is developed to form a plurality of banks 1061 on the black matrix 1021. Spaces are defined by the banks 1061 and the black matrix 1021.
Referring to FIGS. 7 to 8, an ink-drop 108 of a desired color in a micrometer-range size is injected into the spaces defined by the banks 1061 the black matrix 1021, and the ink-drops 108 are mixed together in the spaces to form ink 110.
Referring to FIG. 9, the ink 110 is dried or cross-linked or both by a solidifying device, such as a heating device or a light-emitting device to form a flat color layer 114. The flat color layer 114 may be red for example. Correspondingly, other color layers, such as blue-color layer and green-color layer may be formed adjacently to the color layer 114.
In the conventional method for manufacturing a color filter, for transferring the pattern from the photo-mask to the black matrix 1021, firstly the pattern of the photo-mask is transferred to the first photoresist layer 104 to form the patterned photoresist layer 1041. Secondly the pattern of the patterned photoresist layer 1041 is transferred to the metallic material layer 102 to form the black matrix 1021. Therefore, the pattern precision of the black matrix 1021 may be reduced due to the two-step nature of the process of forming the black matrix 1021. The precision of the banks 1061 and the color layer 114, etc. may also be reduced too. Moreover chromium is harmful to the environment as it is a heavy metal and is toxic to living organisms.
What is needed, therefore, is a method for manufacturing a color filter with high pattern precision for the black matrix.